School sector or student selection? Evidence on foundational skills from Nigeria

Private schooling is expanding rapidly in Nigeria, yet evidence on whether private schools deliver better learning remains mixed. Using data from the 2015 Nigerian Education Data Survey, a nationally representative household-based assessment of nearly 30,000 primary school children in grades two to six, I estimate differences in foundational skill achievement between private and public school students using ordinary least squares (OLS) and propensity score matching (PSM) to adjust for observable differences between students, and instrumental variable estimation and Heckman selection correction to additionally account for unobserved selection into school types. While private schools outperform public schools in raw comparisons, these advantages largely disappear once selection is accounted for, with at most a small literacy advantage and evidence of a numeracy disadvantage remaining after adjusting for unobservables. Heterogeneity analysis reveals that the numeracy advantage in OLS is driven largely by children who do not receive extra tuition at home and disappears for those who do. Among the poorest households, private school attendance is associated with meaningfully higher achievement in both domains once observable selection is addressed. Regional analysis further shows that the private school achievement advantage is concentrated in the South, with no significant advantage observed in the North in either OLS or PSM. Analysis of native language literacy assessments further shows that the English literacy advantage does not extend to native language literacy and is negative among private school students in Northern Nigeria, supporting the interpretation that differential language of instruction rather than superior school quality drives the observed literacy gap. The results suggest that household selection drives most of the observed differences in achievement at the population level, and that the value of private schooling depends critically on household context, with higher achievement concentrated among the poorest and least-supported students.